Clutch-type plates having external or internal splines for engagement with a transmission structure, such as a housing or shell, are typically employed in vehicle transmissions. For example, such plates are used in overrunning coupling assemblies in planetary gearing for automotive transmissions to control the relative motion of the elements of the gearing in order to effect speed ratio changes. Such couplings may act as brakes for anchoring the reaction element of the gearing against rotation in one direction, while permitting rotary motion in the other direction.
An example of an overrunning coupling used as a brake for a planetary gear element in an automotive vehicle driveline may be seen by referring to U.S. Pat. No. 4,938,097 (the '097 patent) where an overrunning coupling is used to transfer planetary carrier torque to a stationary transmission case or housing. When the gearing for the transmission is conditioned for torque delivery, multiple clutches and brakes are used to establish plural torque flow paths through the gearing. When the clutches and brakes are conditioned for low-speed ratio operation, reaction torque is distributed through the overrunning coupling to the transmission housing. Upon an upshift from the lowest ratio speed to the next highest speed ratio, reaction torque on the overrunning coupling is relieved, thereby permitting rotation of the previously anchored planetary gear element. In the case of the structure shown in the '097 patent, the element that is anchored during low-speed ratio operation is the planetary carrier of one of two simple planetary gear sets.
An overrunning coupling that is capable of embodying the improvements of the present invention may be seen by referring to copending patent application Ser. No. 08/871,192, filed Jun. 9, 1997, entitled "Overrunning Planar Clutch Assembly", which is assigned to the assignee of the present invention and which is incorporated by reference.
The planar coupling assembly of the invention of the copending patent application comprises a pocket plate and a notch plate which are arranged in juxtaposed, face-to-face relationship on a common axis. The pocket plate receives a plurality of struts in angularly spaced pockets at locations equidistant from the axis of the coupling. The notch plate has recesses or notches situated at angularly spaced locations at radial positions that coincide with the radial positions of the strut pockets. The pocket plate includes springs that urge the struts into engagement with the notches or recesses in the notch plate so that torque can be transmitted between the plates in one direction, while permitting free-wheeling motion of the plates when the plates rotate relative to one another in the opposite direction.
A planar coupling assembly of the type described in the copending patent application identified above can be used in a transmission to effect underdrive speed ratio operation as driving torque is transferred to one gear element of the transmission. This causes reaction torque to be applied to a reaction element of the transmission gearing. The reaction element is connected to one of the plates of the planar coupling assembly. The companion plate of the planar coupling assembly is splined to the transmission case or housing or other torque transfer member of the transmission. When the transmission is conditioned for underdrive speed ratio operation, the struts of the planar coupling assembly then distribute torque to the transmission case or housing.